The Autism Epidemic: Fact or Artifact?

Objective: We provide an illustration of how changes in methodological factors may produce variations in the frequency of autistic disorder (AD) over time and project how much of the observed increase in the frequency of AD may be explained by methodological factors. Method: Using a prediction analy...

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Bibliographic Details
Published inJournal of the American Academy of Child and Adolescent Psychiatry Vol. 46; no. 6; pp. 721 - 730
Main Authors Wazana, Ashley, Bresnahan, Michaeline, Kline, Jennie
Format Journal Article
LanguageEnglish
Published United States Lippincott Williams & Wilkins 01.06.2007
Subjects
Adolescent
Age
Autism
Autistic Disorder - diagnosis
Autistic Disorder - epidemiology
Child
Child, Preschool
Children
Clinical Diagnosis
Cohort Studies
Cross-Sectional Studies
Diagnostic and Statistical Manual of Mental Disorders
Diagnostic Tests
Epidemiologic Factors
Evaluation Methods
Global Health
Humans
Identification
Incidence
Infant
Infant, Newborn
Models, Theoretical
Prediction
Research Design
Time Factors
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Summary:Objective: We provide an illustration of how changes in methodological factors may produce variations in the frequency of autistic disorder (AD) over time and project how much of the observed increase in the frequency of AD may be explained by methodological factors. Method: Using a prediction analysis, we calculate how broadening diagnostic criteria, younger age at diagnosis, and improved efficiency of case ascertainment could produce temporal trends in the incidence and prevalence of AD, measured by calendar year and by year of birth, in a hypothetical population of children 0 to 18 across the years 1950 to 2020. Results: Time trend studies report an increase as large as 11.0-fold over a 13-year period for AD. Conservative changes in the three methodological factors produced increases in the frequency of AD ranging from 2.1- to 28.8-fold. Measures of frequency by year of birth show the largest magnitude of increase; predicted prevalence by calendar year and to age 4 by year of birth are influenced by changes in the distribution of age at diagnosis, but 1-year incidence and prevalence to age 12 are not. Discussion: Methodological factors may explain the observed increases in AD over time. To increase confidence in reports of time trends, we recommend particular frequency measures and study circumstances. (Contains 2 tables and 1 figure.)
ISSN:0890-8567
DOI:10.1097/chi.0b013e31804a7f3b